Accumulation Sales/Demand History

1. Bucketizing Demand History
For the purposesof analyzing saleshistoryandmakingforecasts,demand forpartsis summarizedinto
buckets. Monthlybuckets seemtobe the mostcommon. However,since notall monthshave the same
numberof days,simplyusingthe month& yearof a demand asthe “bucketizing”index introduces some
unwanted variationintothe monthly demand. Thisvariationmaynotbe large,butit wouldbe nice if it
couldbe eliminated.
Caterpillarattemptedtoeliminate thisvariationbycalculatinghow manyworkingdays there were in a
monthand scalingthe demandtoa standardbase. Mr. D didnot like thisapproach. First, itleadsto
the historical databeingdisplayedasa decimal number. Customerscannotordera decimal quantityof
an item,sothismethodof calculationjust seemsstupid. Second,thisapproachis25 yearsout of step
withthe modernworld. The realitiesof ourglobal interneteconomy meansthatordersfromcustomers
come in 24 hoursa day365 daysa year.
One day Mr. D remembered the existence of Earth’stwinplanet –Caeterus-Terra. Accordingtoan
episode of TheTwilight Zone,Caeterus-Terrahasexactlythe same orbitaroundthe sun as the Earth, but
is½ yearaway fromEarth. Since it movesatthe exactsame speed aroundthe sun as the Earth does
there isno dangerof the two planetsevercolliding. Itisnot observable fromEarth,andwas only
serendipitously discoveredby the Voyager2space craft. Ultimately,NASA launchedVoyager 3to study
planetCaeterus-Terra.
We all knowthat the Earth spinsonits axisonce every24 hours andtakes365 Earth days to circle the
sun. Since the number365 isnot evenlydivisible by12,not all of our earthmonthshave the same
numberof days. Caeterus-Terraspinsonitsaxis slowerthan doesthe earth- an equivalentof every24
hoursand 20 minutes of earthtime. Therefore, sincethe Caeterandayislongerthanearth’sday,
Caeterus-Terratakesonly360 Caeterandaysto circle the sun. To be precise,however, there are only
20 hours ina Caeteranday,but a Caeteranhouris longerthan ours. Most importantly,since the
Caeteranyearis360 dayslongit is divided into12monthsof exactly 30 dayseach.
ConvertingEarthtime toCaeterantime isa snap. Figure 1 showsthe conversion figures forthe firstand
lastday of eachEarth month,and a fewadditional daysthatare boundarydates.

2. Bucketizing Demand History
Earth Date Earth Day
Caeterian
Day
Earth
Month
Caeterian
Month
1/1/14 0:01 1.00 0.98 1 1
1/30/14 0:00 30.00 29.51 1 1
1/31/14 0:00 31.00 30.49 1 2
2/1/14 0:00 32.00 31.48 2 2
2/28/14 0:00 59.00 58.03 2 2
3/1/14 0:00 60.00 59.02 3 2
3/2/14 0:00 61.00 60.00 3 2
3/3/14 0:00 62.00 60.98 3 3
3/31/14 0:00 90.00 88.52 3 3
4/1/14 0:00 91.00 89.51 4 3
4/30/14 0:00 120.00 118.03 4 4
5/1/14 0:00 121.00 119.02 5 4
5/2/14 0:00 122.00 120.00 5 4
5/31/14 0:00 151.00 148.52 5 5
6/1/14 0:00 152.00 149.51 6 5
6/30/14 0:00 181.00 178.03 6 6
7/1/14 0:00 182.00 179.02 7 6
7/2/14 0:00 183.00 180.00 7 6
7/31/14 0:00 212.00 208.52 7 7
8/1/14 0:00 213.00 209.51 8 7
8/31/14 0:00 243.00 239.02 8 8
9/1/14 0:00 244.00 240.00 9 8
9/30/14 0:00 273.00 268.52 9 9
10/1/14 0:00 274.00 269.51 10 9
10/31/14 0:00 304.00 299.02 10 10
11/1/14 0:00 305.00 300.00 11 10
11/30/14 0:00 334.00 328.52 11 11
12/1/14 0:00 335.00 329.51 12 11
12/2/14 0:00 336.00 330.49 12 12
12/31/14 23:59 366.00 360.00 12 12
Figure 1 - Caeteran Date Conversion
Mr. D hopesthatit isintuitivelyobviousthatthisisthe penultimate methodfor the monthly bucketizing
of demand. There couldbe analogous methodswithsomeothernumberof months inayear,but that
wouldbe just silly.
Well there itis:a tasty entrée inMr. D’s smorgasbordof ideas. Take whatyou want,and leave the rest.
Contact Mr. D at MisterD@windstream.net if youhave questions.